1. Field of the Invention
The present invention relates to methods for making dispersable granular forms of salts of water soluble or hygroscopic pesticidal compounds.
2. Background of the Prior Art
Granular formulations of pesticides tend to be safer in application and environmentally, as they are more easily handled by the farmer. Dry, flowable formulations of silica and oil soluble pesticides are known. These formulations are generally adsorbed onto a solid carrier, milled and then granulated. However, this technique is generally unacceptable when attempted for use with water soluble or hygroscopic agricultural products.
The plant growth regulator, known trivially as mepiquat chloride, is a water soluble pesticidal salt and is generally used to control various aspects of cotton boll growth. See, for example, Khafaga, Angew Botanik 57, 257-265 (1983); Sawan et al., J. Agronomy & Plant Science, 154, 120-128 (1985); U.S. Pat. Nos. 3,905,798 and 4,447,255.
As an example, mepiquat chloride has a high water solubility, in general, more than about 600 g/L. The substance is very hygroscopic, readily absorbing moisture from humid air, so that the dry powder can turn to liquid when exposed to ambient humid air. Additionally, the solid material cakes rapidly in storage and sticks to container surfaces, even when initial water contents below 0.5%. These properties make it extremely difficult to granulate and disperse mepiquat chloride, for example.
There is a need for dispersable, granular formulations for water soluble or hygroscopic pesticidal compounds which maintain the biological activity of the water soluble or hygroscopic pesticidal compound.